Suitability of boreal mixedwood clearcuts as wood bison (Bison bison athabascae) foraging habitat in north-central Alberta,Canada

Plant species composition (n = 95) and biomass (n = 62) samples from harvested and natural stands were analyzed to determine if forest clearcutting increased forage abundance for wood bison (Bison bison athabascae) in north-central Alberta. The sampled stands ranged from 1 to 28 and 50 to 100 years old, respectively, and were members of a Populus tremuloides/Rosa-Viburnum vegetation-type, which is a common forest community on upland sites in the boreal mixedwood zone of western Canada. In addition, a five-stand chronosequence was monitored from May to September, inclusive, to measure seasonal variation in forage abundance and nutrient content. Three-fourths of clearcuts were mechanically treated after harvesting. The data showed that clearcutting increased forage availability, but not quality. Peak summer biomass production occurred in 2–12-year-old clearcuts (∼944 kg/ha, S.D. 511, n = 30), with forage availability decreasing to natural stand levels (∼228 kg/ha, S.D. 147, n = 10) 25–30 years after harvesting. Mechanical site treatment increased forage availability by 26% above untreated clearcuts (P = 0.002). No major differences relevant to bison nutrient requirements occurred between forbs and graminoids in summer, or among age-classes within a monitored chronosequence. Crude protein content declined and fiber content increased during the growing season. Peak forage availability and maximum crude protein content occurred in July among monitored stands. Species with fair forage quality dominated the vegetation in 1–16-year-old clearcuts, with the proportion of forbs increasing as stands aged. Maximum summer carrying capacity of natural stands averaged 0.57 animal unit month per hectare (AUM/ha), depending upon the applied assumptions, with lower winter values (0.01–0.03 AUM/ha). In 2–12-year-old clearcuts, maximum summer and winter carrying capacities were <0.67 and <0.29 AUM/ha based on 25% seasonal usage, respectively. The application of a safe-use factor, down-weighting of forbs to account for dietary preferences, and adjustments for forage quality reduced summer (≤0.30 AUM/ha) and winter (≤0.07 AUM/ha) carrying capacities. Wood bison carrying capacity typically decreased when stands were >8 years old. Clearcuts provide adequate forage for wood bison during the summer, but owing to low graminoid biomass they are not suitable as winter habitat.     

Studies on population frequency of insects and mites causing galls on the leaves of the European aspen<Emphasis Type="Italic"> Populus tremula</Emphasis> L. in southern Poland

Species composition of galls on the leaves of Populus tremula L. was studied in 2002–2003 in two localities: the Ojców National Park and the Andrychów Forest District. A total of 2,199 galls were found, 1,522 of which were found in 2003. The galls were caused by ten insect or mite species. The species composition of the galls was similar in these two consecutive years. Phyllocoptes populi (Nalepa) was the most abundant species in both areas in 2003. The index of occurrence frequency (F) value was highest in the case of P. populi, namely 0.280 in the Ojców NP (2003), and lowest , i.e. 0.00002, for Trichiocampus grandis (Lepeletier) at both sites in 2003, and for Contarinia petioli (Kieffer) in the Ojców National Park in 2002. The highest value for Agrells index of species co-occurrence , i.e. 0.944, was found for Harmandia cavernosa (Rübsaamen) and H. tremulae (Winnertz) (Ojców NP, 2002), and the lowest (0.050) for T. grandis and H. globuli (Rübsaamen) (Ojców NP, 2003).     

Contribution of fine roots to ecosystem biomass and net primary production in black spruce, aspen, and jack pine forests in Saskatchewan

Fine root (<2 mm) processes contribute to and exhibit control over a large pool of labile carbon (C) in boreal forest ecosystems because of the high proportion of C allocated to fine root net primary production (NPP), and the rapid decomposition of fine roots relative to aboveground counterparts. The objective of this study was to determine the contribution of fine roots to ecosystem biomass and NPP in a mature black spruce (Picea mariana Mill.) (OBS), aspen (Populus tremuloides Michx.) (OA), and jack pine (Pinus banksiana Lamb.) (OJP) stand, and an 11-year-old harvested jack pine (HJP) stand in Saskatchewan. Estimates of fine root biomass and NPP were obtained from nine minirhizotron (MR) tubes at each of the four Boreal Ecosystem Research and Monitoring Sites (BERMS). Fine root data were collected once a month for May–September in 2003 and 2004. Additional C biomass and NPP data for various components of the forest stands were obtained from Gower et al. (1997) and Howard et al. (2004). Annual fine root biomass averaged 3.10 ± 0.89, 1.71 ± 0.49, 1.62 ± 0.32, and 2.96 ± 0.67 Mg C ha⁻¹ (means ± S.D.) at OBS, OA, OJP, and HJP, respectively, comprising between 1 and 6% of total stand biomass. Annual fine root NPP averaged 2.66 ± 0.97, 2.03 ± 0.43, 1.44 ± 0.43, and 2.16 ± 0.81 Mg C ha⁻¹ year⁻¹ (means ± S.D.) at OBS, OA, OJP, and HJP, respectively, constituting between 41 and 71% of total stand NPP. Results of this study indicate that fine roots produce a large amount of C in boreal forests. It is speculated that fine root NPP may control a large amount of labile C-cycling in boreal forests and that fine root responses to environmental and anthropogenic stress may be an early indicator of impaired ecosystem functioning.     

Effects of soil temperature and time of decapitation on sucker initiation of intact Populus tremuloides root systems

Abstract

In a growth chamber experiment, root suckering of aspen (Populus tremuloides Michx.) was assessed in relation to timing of cutting and soil temperature. Aspen seedlings were grown in large pots for 3 years before experimentation. In a 2×2 factorial experiment, 3-year-old seedlings were cut at the end of the dormant period or after leaf flush and grown at two soil temperatures (8 or 20°C) for 39 days. Root systems were evaluated for suckering response and carbohydrate reserve status. There were no differences between the two soil temperatures and times of cut in the number of sucker buds initiated on the roots, but the number of buds that developed into suckers was much greater at 20°C. Cutting the dormant seedlings delayed suckering by nearly a week, resulting in smaller suckers at the time of harvest. However, cutting the seedlings when dormant produced almost twice the number of suckers than when cutting occurred after leaf-out. Total non-structural carbohydrates (TNC) of roots declined from 35.6% of dry weight at the end of the dormant season to 21.6% at the time of leaf-out, but there were no differences between the soil temperature and timing of cut treatments. After the 39 day growth period, root systems had 7% lower root TNC in the 20°C treatment than in the 8°C treatment, likely to support the development of the emerging suckers and higher respiration demands.     

杨树伐根嫁接山杨改造虫毁林试验简报

近年来,杨树枝梢害虫在互助县严重发生,导致成片虫毁林的出现。我们利用杨树伐根嫁接山杨进行试验,取得了成功,山杨适应性强,生长快,并且抗枝梢害虫的特性十分突出,是更新现有虫毁林的理想树种,值得大力推广。     

Impacts of elevated CO2 and O3 on aspen leaf litter chemistry and earthworm and springtail productivity

Human alteration of atmospheric composition affects foliar chemistry and has possible implications for the structure and functioning of detrital communities. In this study, we explored the impacts of elevated carbon dioxide and ozone on aspen (Populus tremuloides) leaf litter chemistry, earthworm (Lumbricus terrestris) individual consumption and growth, and springtail (Sinella curviseta) population growth. We found that elevated carbon dioxide reduced nitrogen and increased condensed-tannin concentrations in leaf litter. These changes were associated with decreases in earthworm individual growth, earthworm growth efficiency, and springtail population growth. Elevated ozone increased fiber and lignin concentrations of leaf litter. These changes were not associated with earthworm consumption or growth, but were associated with increased springtail population growth. Our results suggest that changes in litter chemistry caused by increased carbon dioxide concentrations will have negative impacts on the productivity of diverse detritivore taxa, whereas those caused by increased ozone concentrations will have variable, taxon-specific effects.     

Regeneration of Populus nine years after variable retention harvest in boreal mixedwood forests

Aspen and balsam poplar regeneration from root suckers were assessed in boreal mixedwood forests nine years after logging in a variable retention experiment (EMEND Project—Ecosystem Management Emulating Natural Disturbance) located north of Peace River, Alberta, Canada. Five levels of retention of mature trees (2%, 10%, 20%, 50% or 75% of the original basal area) were applied in stands dominated by aspen, white spruce or mixtures of the two species. Basal area of aspen (or that of aspen plus balsam poplar combined) prior to logging strongly influenced sucker density of aspen (or aspen + balsam poplar combined) and in some cases their growth. Nine years after harvest there was a decline in sucker density and volume ha⁻¹ with increasing retention levels of aspen (or both poplars combined); sucker density declined by 50% when only 20% of the original basal area was left in the stand. Retaining mature spruce trees in the stand had little influence on the number of suckers but did affect their total volume ha⁻¹. Thus, we suggest that by knowing stand aspen and balsam poplar density prior to logging and varying levels of retention of aspen and balsam poplar or conifers at harvest, the density of Populus regeneration can be predicted by managers, thereby allowing them to create a range of mixedwood conditions.     

Heat treatment of wet wood fiber: A study of the effect of reaction conditions on the formation of furfurals

Abstract

Furan monomers are produced when wood is heated at high temperatures. To understand the process conditions for production of furfural (FF) and hydroxymethylfurfural (HMF) from wood, samples of milled aspen wood were subjected to autohydrolyzis by microwave heating in a sealed Teflon reactor. The experiments were designed to simulate temperature and pressure variables of a fiberboard press and their effect on production of furans from the hemicelluloses that have the potential for promoting self-bonding of the wood fibers. The effect of a Lewis acid catalyst, AlCl₃·6H₂O on the formation of FF and HMF was also studied. The hydrolysates were analyzed for the liberated wood sugars and dehydration products, FF and HMF. The FF and HMF yields under autohydrolyzis conditions increased with increase in severity factor, CS. Under catalyzed hydrolyzis conditions, the FF yield decreased, while the HMF yield increased with increase in severity factor. Under catalyzed hydrolyzis conditions the FF yield decreased presumably due to degradation reactions including resin formation. The increase in HMF yield with increasing severity factor was most likely due to hydrolyzis of glucan from cellulose. These results suggest that FF and resin yields could be enhanced with the addition of a Lewis acid catalyst to the wood particles, but that process variables need to be controlled in order to avoid or minimize degradation of the wood cellulose.     

基于Aspen HYSYS的沼气中CO2气体低温液化分离技术

基于沼气主要成分CH4气体和CO2气体物理性质的差异,利用PR方程,得出不同CH4体积分数下,沼气泡点和露点的温度和压力;在Aspen HYSYS平台中,设计了低温液化分离沼气中CO2气体的流程,仿真分析了低温液化对CH4体积分数和CO2体积分数的影响.根据低温液化分离沼气中CO2气体的流程,对沼气进行纯化实验,结果表明:实验结果与模拟结果相吻合;液化分离后CH4体积分数从58.2％升至82.8％,CO2体积分数由36.4％降至8.8％,N2+ O2体积分数小于4.0％.     

A proximity-based approach to assessing habitat

Planning for either a single species, multiple species, or ecosystems is greatly dependent on spatial interactions in the landscape. Problems exist for evaluating wildlife habitat changes over large ranges of space and time. This paper illustrates the use of Geographic Information Systems (GIS) to evaluate habitat for a single species, ruffed grouse (Bonasa umbellus), following a time series of forest harvests. A habitat suitability model for ruffed grouse is utilized on a two-township study area in north-central Minnesota to assess the habitat suitability changes over time using an even-aged area-control harvesting plan. The results are presented as a habitat quality change map and a contingency table, representing the movement of habitat class areas between time periods resulting from the proposed harvesting. We developed a neighborhood definition to allow for spatially varying habitat values. This work illustrates the ability to look ahead and around in estimating the impact on wildlife habitat resulting from alternative future management activities.Now with the U.S. Forest Service, Sitka, AK 99835.